In the past, it was the general practice to complete oil and gas wells by providing a casing hanger system that is provided at or near the surface of the earth. Many land wells are still completed in this manner with excellent success. With the advent of offshore drilling in order to produce petroleum products from production zones located beneath bodies of water, it has become desirable to provide well casing hanger systems that are adapted to be positioned at or near the bottom of the body of water. With the development of the hanger systems of U.S. Pat. Nos. 3,287,030 and 3,405,763, and other U.S. patents, it has become practical to provide well completion systems, typically known as "mud line suspension systems," that enable the location of well casing suspension systems at or near the bottom of bodies of water. Moreover, thse mud line suspension systems also enable the driller to pull away from the well being drilled when circumstances necessitate doing so and subsequently reestablish a well drilling connection with the subsea well casing suspension system when it is desirable to continue drilling operations. By locating well suspension systems at or near the ocean floor, a temporarily abandoned well or capped well does not present an obstruction that typically interferes with the marine environment. Such suspension systems also enable the driller to complete wells by means of an ocean floor completion or extend the conduits to the surface for completion on platforms and consequently lends a degree of flexibility in completion systems that renders such hanger systems desirable.
As is evident from U.S. Pat. No. 3,287,030, subsea suspension systems are also effectively provided with wash ports that enable casing cement to be washed from the hanger system in order that the casing cement does not interfere with subsequent connection and disconnection of well completion conduits to the casing hanger assembly.
In order to establish a locked interconnection between the hanger system and inner casing that is supported by the hanger, U.S. Pat. Nos. 3,420,308; 3,424,477; 3,893,717; and 3,972,546 incorporate weight energized locking mechanisms that establish a weight supporting function to transfer the load of inner supported casing to outer supporting casing. Further, these patents disclose shearable elements that assist in controlling activation of the locking mechanisms and, in some cases, as in U.S. Pat. No. 3,420,308, also function to provide a weight supporting function for the locking mechanism. Other patents of interest to well hanger systems for underwater completion include U.S. Pat. Nos. 3,287,030 and 3,405,763. A more recent development in undewater well completion systems is exemplified by U.S. Pat. No. 4,053,023. It is a feature of the present invention to provide a novel casing hanger suspension system for completion of wells, such as underwater wells, wherein a locking mechanism is employed in the casing hanger automatically releasable and weight energized locking system for establishing interconnection between inner and outer casings of the casing hanger system.
It is also a feature of the present invention to provide a novel casing hanger system wherein an expandable locking ring is employed to establish an interconnection between inner and outer casings and the weight of the inner casing is supported by the locking ring and by a lock positioning ring that is also weight energized to expand radially into supporting relation with the wall surface of the outer casing.
It is also a feature of this invention to provide a novel locking mechanism for well casing hanger assemblies wherein a lock positioning ring is employed that is capable of automatically retracting to a noninterfering position in the event the inner pipe is moved upwardly for removal from the outer pipe of the casing hanger system.
Still a further feature of this invention concerns the provision of a novel locking mechanism for well casing hanger assemblies and which is transported along with the inner pipe being inserted into an outer pipe of the casing hanger assembly by means of a shearable or mechanically interconnected relation with the inner pipe structure.
Other and further objects, advantages and features of this invention will become obvious to one skilled in the art upon an understanding of the illustrative embodiment about to be described and various advantages, not referred to herein, will occur to one skilled in the art upon employment of the invention in practice.